Investigating the trade-off between operating revenue and CO2 emissions from crude oil distillation using a blend of two crudes

Blending of different crude types is frequently used in petroleum refineries to improve their profitability and products yields. However, energy consumption and consequential CO₂ emissions strongly depend on the types of crude being processed. The trade-off between CO₂ emissions and economic objectives, such as net revenue, is investigated for cases of different crude blends using the multi-objective optimization approach. The first objective is the minimization of CO₂ emissions whilst the second objective is maximizing the net revenue from the crude distillation unit (CDU). A rigorous model is used to estimate CO₂ emissions from different sources within the CDU. This emissions model incorporates pinch analysis for heat integration, to optimize the distribution of utilities related to emissions. Blends of two crudes, 36 API and 27.7 API, are used as feedstock to a rigorous CDU model of the atmospheric crude tower, vacuum tower and heat exchanger network. Lighter crude blends recorded higher CO₂ emissions and net revenue compared with the heavier blend due to the greater distilled fraction. However, CO₂ emissions did not vary linearly with the fraction of each crude, as the heat exchanger network also influenced the degree of heat recovery and consequently the level of CO₂ emissions. The multi-objective solutions show the influence of all 13 of the process variables on the objectives.     

Effects of the difference in electrical resistance under the land and channel in a PEM fuel cell

Previous studies have shown experimentally that the current density in a proton exchange membrane (PEM) fuel cell can be significantly higher under the land than under the channel in most practical operating cell voltage ranges [14]. In order to determine if the difference in electrical resistances under the land and the channel is a major cause for the observed local current density differences, a dedicated experimental study has been conducted to separately measure the electrical resistance under the land and channel and to isolate the in-plane (lateral) resistance from the total resistance of the gas diffusion electrode (GDE). First, a special test fixture is designed such that the electron paths under both the land and the channel are identical to those in a real operating fuel cell and the electrical resistance under each area can be measured separately. Using this test fixture, the total electrical resistances under the land and the channel are measured separately. The results show that the total electrical resistance under the channel is much higher than that under the land except in the case with very narrow channels. Secondly, in order to determine the source(s) of the difference in electrical resistance under the different areas, the in-plane resistances of the GDE and the gas diffusion layer (GDL) are measured. The results show that the difference in lateral resistance between the areas under the land and the channel is negligibly small. Thirdly, basic analyses show that the difference in direct voltage loss caused by the higher electrical resistance under the channel is significant; besides, the resistance difference can result in a large enough variations in local overpotential to cause significant local current density differences. Therefore, the difference in local electrical resistance under the land and channel is large enough to be a major cause for the observed local current density differences.     

Characterization of Crude Oils and Their Fouling Deposits Using a Batch Stirred Cell System

A small (1 L) batch stirred cell system has been developed to study crude oil fouling at surface temperatures up to 400°C and pressures up to 30 bar. Fouling resistance–time data are obtained from experiments in which the principal operating variables are surface shear stress, surface temperature, heat flux, and crude oil type. The oils and deposits are characterized and correlated with the experimental heat transfer fouling data to understand better the effects of process conditions such as surface temperature and surface shear stress on the fouling process. Deposits are subjected to a range of qualitative and quantitative analyses in order to gain a better insight into the crude oil fouling phenomenon. Thermal data that can be obtained relatively quickly from the batch cell provide fouling rates, Arrhenius plots, and apparent activation energies as a function of process variables. The experimental system, supported by computational fluid dynamics (CFD) studies, allows fouling threshold conditions of surface temperature and shear stress to be identified relatively quickly in the laboratory. The data also contribute to existing knowledge about the compensation plot.     

Environmental contingency in life history strategies: The influence of mortality and socioeconomic status on reproductive timing.

Why do some people have children early, whereas others delay reproduction? By considering the trade-offs between using one's resources for reproduction versus other tasks, the evolutionary framework of life history theory predicts that reproductive timing should be influenced by mortality and resource scarcity. A series of experiments examined how mortality cues influenced the desire to have children sooner rather than later. The effects of mortality depended critically on whether people grew up in a relatively resource-scarce or resource-plentiful environment. For individuals growing up relatively poor, mortality cues produced a desire to reproduce sooner—to want children now, even at the cost of furthering one's education or career. Conversely, for individuals growing up relatively wealthy, mortality cues produced a desire to delay reproduction—to further one's education or career before starting a family. Overall, mortality cues appear to shift individuals into different life history strategies as a function of childhood socioeconomic status, suggesting important implications for how environmental factors can influence fertility and family size. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Topology optimization of periodic layouts of dielectric materials

A topology optimization method is used to design two dimensional periodic structures with desirable transmission properties by distributing two materials of different permittivity over a rectangular representative cell. A plane wave expansion of the electric field at the input and output boundaries is used in the analysis. This allows non-homogeneous material distributions near the boundaries. Numerical examples are used to verify the robustness of the method and to investigate the importance of retaining higher modes in the expansions. It is found that the optimization problem typically admits possibly many local optima and the relevance of higher modes depends on the nature of the solution found. In some instances, higher modes play an important role and using only the dominant mode in the analysis is shown to result in errors in the evaluation of the performance of the design.     

Full-field feed-forward equalizer with adaptive system optimization

We numerically investigate the combination of full-field detection and feed-forward equalizer (FFE) for adaptive chromatic dispersion compensation up to 2160 km in a 10 Gbit/s on–off keyed optical transmission system. The technique, with respect to earlier reports, incorporates several important implementation modules, including the algorithm for adaptive equalization of the gain imbalance between the two receiver chains, compensation of phase misalignment of the asymmetric Mach–Zehnder interferometer, and simplified implementation of field calculation. We also show that in addition to enabling fast adaptation and simplification of field calculation, full-field FFE exhibits enhanced tolerance to the sampling phase misalignment and reduced sampling rate when compared to the full-field implementation using a dispersive transmission line.     

Engineering the system of communication for safer surgery

Communication failures are a leading cause of error in surgery. Researchers and practitioners have therefore developed different interventions to improve communications, such as team briefing and pre-operative patient checklists. These different methods have clear merit. However, they have only dealt with portions of a complex system. Consequently, disparate interventions of varying kinds may not integrate and build an effective system of communication. We argue that a new view of communication is needed to improve safety in surgery; the view that communication is more fundamentally as a property of the whole system of work rather than confined to interpersonal exchanges. Rather than simply add an intervention to the system, interventions should integrate into the system. To achieve this, we propose a practical strategy to re-engineer the system of communication for surgery. This demands an analysis of the immediate informational needs within the system of interest, and an account of the wider system and those ergonomic and human factors shaping the performance of communicators. We illustrate the application of the method and refer to potential improvements in safety.     

The mediating role of coping: A cross-sectional analysis of the relationship between coping self-efficacy and coping effectiveness among athletes.

This study examines the relationship among global coping self-efficacy, coping, and coping effectiveness within athletes. We hypothesized that there would be a positive association between coping self-efficacy and coping effectiveness, which would be mediated by coping. It was also predicted that coping strategies within the task-oriented coping dimension would be positively associated with coping effectiveness, whereas strategies from the disengagement- and distraction-oriented coping dimensions would be negatively associated with coping effectiveness. Participants were 353 athletes between the ages of 18 and 29 years, who completed a measure of coping self-efficacy the night before they competed, in addition to a measure of the athletes' use of coping strategies and their perceived coping effectiveness, which was completed immediately after the competitive event. Results revealed that higher global coping self-efficacy scores were significantly (r = .33, p     

FIB与PEM联用在半导体器件失效分析中的应用

在半导体器件的失效分析中,缺陷定位是必不可少的重要环节.光发射显微镜(PEM)是IC失效定位中最有效的工具之一.PEM利用了IC器件缺陷在一定条件下的发光现象,迅速定位缺陷.而聚焦等离子束(FIB)的定点切割和沉积技术在亚微米级半导体工艺失效分析中扮演着越来越重要的作用.介绍了一种联合使用FIB和PEM进行亚微米级缺陷定位的新方法,使得一些单独使用PEM无法完成缺陷定位的案例得以成功解决.     

High-density automotive hydrogen storage with cryogenic capable pressure vessels

LLNL is developing cryogenic capable pressure vessels with thermal endurance 5–10 times greater than conventional liquid hydrogen (LH₂) tanks that can eliminate evaporative losses in routine usage of (L)H₂ automobiles. In a joint effort BMW is working on a proof of concept for a first automotive cryo-compressed hydrogen storage system that can fulfill automotive requirements on system performance, life cycle, safety and cost. Cryogenic pressure vessels can be fueled with ambient temperature compressed gaseous hydrogen (CGH₂), LH₂ or cryogenic hydrogen at elevated supercritical pressure (cryo-compressed hydrogen, CcH₂). When filled with LH₂ or CcH₂, these vessels contain 2–3 times more fuel than conventional ambient temperature compressed H₂ vessels. LLNL has demonstrated fueling with LH₂ onboard two vehicles. The generation 2 vessel, installed onboard an H₂-powered Toyota Prius and fueled with LH₂ demonstrated the longest unrefueled driving distance and the longest cryogenic H₂ hold time without evaporative losses. A third generation vessel will be installed, reducing weight and volume by minimizing insulation thickness while still providing acceptable thermal endurance. Based on its long experience with cryogenic hydrogen storage, BMW has developed its cryo-compressed hydrogen storage concept, which is now undergoing a thorough system and component validation to prove compliance with automotive requirements before it can be demonstrated in a BMW test vehicle.